These days, friends, friends and WeChat groups can always see everyone’s concern about nucleic acid detection and discuss the COVID-19 epidemic. Since then, nucleic acid detection has become a high-frequency word. But do you really know about nucleic acid testing? What is the nucleic acid strategy under the most severe and complicated situation faced by Chongqing since the COVID-19 epidemic?
In this issue of "Knocking on the Blackboard", Xiaobian will focus on these issues.
The role of nucleic acid detection—It is recognized by the medical communityThe "Gold Standard" for Diagnosing Covid-19
Why do you want to do nucleic acid testing? On November 27th, at the 150th press conference on the prevention and control of COVID-19 epidemic in Chongqing held by Chongqing Municipal Government Information Office, Li Pan, deputy director of Chongqing Municipal Health and Wellness Committee, once again stressed clearly:
Nucleic acid detection is the "gold standard" recognized by the medical community in diagnosing Covid-19. It is an important measure to quickly find infected people, lock the source of infection in time, and quickly cut off the route of transmission. It is a key measure to realize early detection, early reporting, early isolation and early treatment.
(Related links: press conference, responding to concerns-will you be infected in the process of making nucleic acid? What is the difference between regional nucleic acid and expanded nucleic acid?)
At the 147th press conference on November 22nd, Luo Fei, an expert from Chongqing CDC, made an analogy.
If antigen testing is an auxiliary team and nucleic acid testing is the main player; antigen testing is an attack by innuendo, then nucleic acid testing is the final word.
(Related links: press conference, responding to concerns-which is more useful, antigen or nucleic acid? Is the nucleic acid test result true?)
From a professional point of view, the positive result of nucleic acid detection can be regarded as the same as the result of virus culture and then detection. Covid-19 nucleic acid detection is to select two or three characteristic sequences on the virus genome, copy and amplify them, and then detect and compare them, which is what we often call double-target or triple-target detection.
Because the conservative gene sequence of virus is usually selected as the target gene in nucleic acid detection, even if the virus mutates, it has little effect on the detection ability. Nucleic acid detection requires high detection reagents, detection facilities and equipment, and requires professionals to complete more complicated processes such as collection and detection.
- Xiaobian analogy-
- Nucleic acid testing is like "raising a baby chicken". When the chick is very young, most people can’t see the male and female, but when the chick is raised, you will know it when you look at the comb.
- Why does it take several hours for nucleic acid testing to produce results? In fact, it is to cultivate viruses, or to raise chickens. Covid-19 nucleic acid detection is equivalent to using cockscomb as a feature to identify male and female, which is the so-called "target gene". At the same time, it is not easy to misjudge if it is characterized by cockscomb, but it is easy to misjudge if it is characterized by chicken feet and tail, so cockscomb is the so-called "conservative gene".
At the 151st press conference on November 27th, Liao Pu, director of the Laboratory Department of Chongqing People’s Hospital and deputy director of Chongqing Clinical Laboratory Center, also explained the nucleic acid detection.
(Related links: Why is nucleic acid detection the "gold standard"? What about "false yin" and "false yang")
At present, Covid-19 nucleic acid detection usually uses fluorescence PCR amplification technology, and its principle is that viral nucleic acid is increased exponentially through one cycle, so as to realize Covid-19 nucleic acid detection. This is a very classic and reliable nucleic acid detection method, and it is a technology that won the Nobel Prize.
In the detection process, the yin and yang of the detection results are objectively judged by the circulating threshold of nucleic acid amplification, that is, Ct value. The Ct value is related to the viral load of the infected person. The lower the Ct value of the infected person, the higher the viral load of the infected person. Conversely, the higher the Ct value, the lower the viral load of the infected person.
For the report of positive results, according to the detection strategy, one or two other nucleic acid detection reagents that are more sensitive and amplify different regions will be used to detect the original samples when necessary, and the positive results will not be reported until they are confirmed, so sometimes the detection time is longer.
Although nucleic acid detection technology is the recognized gold standard in Covid-19, it is an internationally recognized detection technology for mature pathogens. However, the so-called "false negative" may appear in unreasonable sample collection, transportation and processing, too low virus droplets in the sample, variation of the target sequence to be detected or sequence change caused by other reasons.
For sudden and new subtype Covid-19, such as Omicron mutant, which has the characteristics of concealment, the optimal sampling time for detection may not be confirmed. In addition, in the process of sample collection and detection, pollution caused by aerosol will occur, resulting in false positive. By strengthening laboratory quality control, monitoring laboratory environment and equipment pollution, and multiple rounds of nucleic acid screening, we minimize the errors caused by technical reasons.
Strategies for nucleic acid detection-different strategies at different stages according to the needs of epidemic situation.
These days, users always leave messages asking questions. Why do you do nucleic acids in different areas?
Indeed, since November 1, especially since November 12, when the coordinated prevention and control of the central city was carried out and the epidemic annihilation war was launched, the Chongqing epidemic prevention and control headquarters adopted different nucleic acid detection strategies at different stages according to the needs of the epidemic situation.
For example, the social inspection has been carried out once every seven days, once every day and every other day. After the city launched the social clean-up attack, according to the deployment of classified attack, all districts and counties were divided into three categories: relatively stable epidemic situation, fluctuating platform period and severe situation, to carry out nucleic acid testing.
Li Pan spoke carefully at the press conference on the evening of November 26th. Under the provisions of the ninth edition and Article 20, various localities will formulate different strategies according to the situation of this area, street, community and even community. Specific to this round of epidemic in Chongqing:
At the beginning of the epidemic, the central city of annihilation was fought-
The epidemic situation is multi-point, multi-source and multi-chain. I don’t know where the potential infected people are, and the chain is unclear. For example, "I don’t know where the’ enemy’ is", then take the whole central city as a whole and carry out nucleic acid testing all over the region, and do it every day, which is to find out the potential infected people. After searching for a period of time, I marked a high-risk area.
Fight the tough battle in the central city in the stage of social clearing-
At this time, it is: high-risk areas should be zoned quickly, and nucleic acid testing should be carried out at the specified frequency in high-risk areas; in other areas, because there is still community transmission, it is necessary to "check every other day" and strive to promote social clearing.
Yuzhong, Jiulongpo, Jiangbei and Yubei made three rounds in three days-
Li Pan said at the press conference on the evening of November 26th that the epidemic situation in all districts of the central city was divided, and some districts added thousands of people a day, with a high proportion of society.
Therefore, just like the annihilation war at the beginning of the epidemic, Yuzhong District, Jiulongpo District, Jiangbei District and Yubei District decided to make three rounds in a row for three days, and continue to exert their strength and concentrate their efforts to find out the potential infected people and the risk sources in a short time.
Similarly, the same is true of Liangping, Dianjiang and Xiushan. The difference is that it is not the whole district (county), but the streets where the county is located and the streets involved in the epidemic.
Xiaobian said so much, we can see that the nucleic acid strategy must be a specific arrangement made according to the current epidemic situation. It is about strategy and actual situation. I hope parents will understand and support it.
Organization of nucleic acid detection-this is an important link, and the organizer must pay attention to it.
This point, Xiao Bian should remind the organization unit of nucleic acid detection, because it is really important.
The organization of nucleic acid detection directly affects the detection quality and screening effect. Staff organization, testing resource allocation, testing object organization, and centralized sampling or sampling by building, unit and floor are all important factors.
For example, on November 26th, some districts and counties reported that "nucleic acid test samples were left behind", which may affect the accuracy and quality of nucleic acid screening for whatever reason, indicating the importance of organizational work.
At the same time, there are still many people who are concerned about the organizational level of nucleic acid testing institutions and the professional ethics of staff, which will also directly affect the testing quality and screening effect.
For the sake of everyone’s health and this city, please ask the organizers of nucleic acid testing to follow the process, make the work meticulous and put the management in place! Please!
(Related links: press conference, responding to concerns-Is nucleic acid testing true or not? Are you sure?)
Can nucleic acid be infected? Everyone should take personal protection, so don’t worry about it.
This point, Li Pan also made a detailed introduction. In fact, you don’t have to worry about doing nucleic acid testing and being infected.
Statistics show that more than 60% of the newly infected people are residents of the same building, the same neighborhood and the same community. The route of infection is often in community activities, with acquaintances and friends, shopping together, and taking express mail together (among them, infected people), without protection or standardized protection and contact.
However, there are very few cases of infection directly in the queue of nucleic acid collection or in the process of nucleic acid collection, but the results of flow adjustment are not supported, so don’t worry.
For high-risk areas, there are positive buildings and units that are tested at home, not to mention worrying.
Look, really don’t worry too much. As long as everyone takes personal protection and adheres to the "one meter distance", this situation can be put an end to.
(Related links: do nucleic acid, remember "5321"!)
Supervision of nucleic acid detection-never be soft when it comes to the end, and please continue to supervise the general public.
On November 24th, at the 148th press conference, Dan Yanzheng, deputy mayor of Chongqing Municipal Government, commander of the municipal epidemic prevention and control command department and director of the comprehensive office, said: At present, the results of nucleic acid testing in the whole city are authentic, so please rest assured.
He said-
Chongqing Municipal Party Committee and Municipal Government have always attached great importance to the quality of nucleic acid detection. In this round of epidemic, in view of the laboratory quality problems with a large amount of detection and public concern, on the basis of monthly laboratory quality assessment and quality control spot check in the early stage, the Municipal Health and Health Commission strengthened management supervision, with municipal quality control experts "conducting daily inspections" and district and county experts "guiding at the station", participating in laboratory management throughout the process, and promptly urging and rectifying problems such as irregular management and process of individual laboratories.
For violations of laws and regulations, we will maintain a high-pressure situation, and immediately start the investigation procedure according to law for the detection errors reflected by the public. Once found, hell to pay.
Ability of nucleic acid detection-Thanks to the strong support of brother provinces and cities, the ability of nucleic acid detection in Chongqing has been enhanced.
Everyone must have noticed that the staff and volunteers of nucleic acid detection are very hard: airtight protective clothing is worn for most of the day or even a day; alcohol cleaning gloves are constantly rubbed, cotton swabs are torn open and carefully sampled …
Especially in the face of this round of large-scale epidemic and large-scale nucleic acid detection, the whole nucleic acid detection system in our city is facing the pressure of long-term and full-load operation, and there are problems such as staff fatigue, high-speed operation of nucleic acid system and obvious lack of detection ability.
In this regard, under the guidance and support of Chongqing Working Group of the State Council Joint Prevention and Control Mechanism, Chongqing has received strong support from some brother provinces and cities, which has enhanced the strength of nucleic acid detection in our city.
(Related links: Medical teams from 8 provinces and cities in China rushed to Chongqing and successively entered Cuntan and Yuelai Fangcang Hospital to carry out medical treatment.)
What should we do-participate in nucleic acid testing as required!
Li Pan said that the majority of medical workers are fighting hard, hoping to eliminate the doubts of some citizens through continuous efforts and higher-quality nucleic acid testing.
What should we do personally to support nucleic acid testing? It’s simple—
Participate in nucleic acid testing as required! This is not only responsible for personal health, but also the need to prevent others from being infected.
At present, the incubation period of Covid-19 is usually 2-4 days, the shortest may be 1 day, or even less than 1 day, and the longest may be 8 days. Therefore, the management policy for close contacts is "5+3" (5 days of centralized isolation and 3 days of home observation) to minimize risks.
The high-risk area is managed by this scientific law, and it will be reduced to a low-risk area after 5 days without sunshine. But this does not mean that there is no risk, and we must continue to observe. If there is mobility, contact, activity and aggregation in the high-risk area, it will cause new infections. If there is a new positive test, the time will be recalculated.
Therefore, lifting the high-risk area does not mean unsealing, but also strengthening observation. In particular, the current epidemic situation in the central city is still severe and complicated, and it is still the coordinated prevention and control of the central city and the implementation of social control.
Here, Xiaobian asks everyone to understand, support and cooperate with various prevention and control measures as always, especially for nucleic acid testing-
Dear friends, don’t give up and refuse the nucleic acid you should do. Only by doing a thorough examination can you find the infected person as soon as possible, block the transmission chain, win a complete victory in the annihilation war as soon as possible, and return to the fireworks of this city as soon as possible.
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On the same day, sanhe city, Hebei Province issued a message, demanding that commuters should be well managed, and commuters can pass by scanning the "Three Rivers Epidemic Protection Pass" when they return, and no longer require daily nucleic acid testing. Xinji city made it clear that the above adjustments will be implemented from July 5th. The grassroots doctors’ commune noted that the suspension of normalized nucleic acid screening in many cities at the same time was mainly based on the "Several Measures on Comprehensively Implementing the Ninth Edition of the Prevention and Control Plan and Scientifically and Accurately Doing a Good Job in Epidemic Prevention and Control" issued by the Health and Health Commission of Hebei Province on July 2. The document is clear:In areas where there is no epidemic, in principle, weekly preventive nucleic acid screening for all staff is not carried out. 
Besides,For those who enter Hebei in areas without epidemic risk, the negative certificate of nucleic acid detection within 48 hours will no longer be checked, and the landing nucleic acid detection will no longer be implemented.Hebei Province requires that all localities and departments should implement the requirements of the Prevention and Control Plan (Ninth Edition) to the letter, immediately adjust relevant prevention and control measures as required, and resolutely prevent the phenomenon of layer upon layer overweight. If the previously issued epidemic prevention and control policies and measures are inconsistent with the Prevention and Control Plan (Ninth Edition), they shall be implemented in accordance with the Prevention and Control Plan (Ninth Edition) and this notice. 
In order to ensure the simplification of epidemic prevention and control, "one size fits all" and "layers of overweight", the state requires all provinces to announce the channels for complaints and reports from the masses and accept extensive supervision from all walks of life. According to the incomplete statistics of grass-roots doctors’ commune, up to now, the following provinces (cities, districts) have announced the complaint reporting methods about the overweight problem of local epidemic prevention and control. 
Although the epidemic has not been completely extinguished, compared with Covid-19, the act of wanton overweight and absurd self-protection is even worse. 
